Catalytic conversion of hydrocarbon oil



Feb. 18, 1947.

. w A.-scHuLzE Erm. CATALYTIC CONVEHSILON OF HYDROCRBO OIL Filed sept.18, 19444 n ommmmazoo BOLVNOLLOVHd aolvavd s provided.)

Other obiects and advantages will be apparent.

Patented Een. 1s, 1947 CATALYTIC CONVE CABBO RSION F HYDRO- N OIL WalterA. Schnlae'and Carl J. Helmers, Bartlesville, Okla., assigncrs toPhillips I etroleum Company, 'a corporation of Delaware ApplicationSeptember 18, 1944; Serial No. 554,845

' ,4 claims. (c1. zoo-ass) This invention relates to a process forconverting hydrocarbon fractions into substantial yields of lightunsaturated hydrocarbons with the simultaneous;l production of valuablestabilized distillate. In one of the more particular applications. thepresent invention relates to controlled catalytic cracking of normallyliquid hydrocarbon materials such as gas oil, kerosene and naphtha toproduce normally gaseous olens 'and diolefins with concurrent productionof by-product distillates rich in aromatic hydrocarbons.

Generally speaking, in the refining practice of the past, catalyticcracking processes have been concerned with the manui'actureof highyields of superior motor fuels. A recognized advantage of such processeshas been the production and conversion of high percentages of gaseousolens to higher boiling hydrocarbons. However. with the advent of recentdevelopments in the design of aircraft engines, the demand for specialhighquality fuels shifted refining technology from motor fuel productionto the manufacture of aviation gasoline. The need for the latter fuelshas created a demand for light oleilns suitable for use in theproduction of alkylate gasoline and for aromatic hydrocarbons valuablefor their favorable efiect on the rich-mixture perfomance of aviationgasoline. Existent catalytic processes have partially solved thisproblem in that distillates rich in aromatic hydrocarbons have beenproduced, but this has been accomplished at the expense of potentialoleiln and diolen production. Since operating variables favorable to onereaction are unfavorable to the other, a denite lack oi exibility isevident in catalytic cracking processes described heretofore.

It is anobject of the present invention to provide a process for thecatalytic conversion of hydrocarbon oils to substantial yields of lightoleilns and diolefins with the simultaneous production of a high qualityaviation blending stock.

Anotherobject of this invention is to provide a catalytic crackingprocess for hydrocarbon oils 'wherein novel means of control oftemperature and contact time within the catalyst zone `is fromthe'followlng disclosure.

We'have now discovered that with the application of thepresentinvention, normallyliquid petroleum hydrocarbons such as gas oil,kerosene and/or naphtha may vbe catalytically treated under reactionconditions leading to the production of valuable light olefins anddioleflns in'substantial yield along with concurrently valuable 2aromatics-contalning distillates. This unusual result is realizedthrougheilective control of temperature and contact time in dierentsections of the catalyst bed. Thus when the catalyst case f' is arrangedfor downward ow, a relatively long contact time at conversiontemperature in the upper portion of the catalyst case favors theformation of a large proportion of-C4 and lighter hydrocarbons alongwith the considerable conversion of the feed to aromatic types, while at,one or more suitable points along the length of the bed a largeproportion oi' heat-carrying steam or other inert diluent is introduced.This diluent, heated to a desired temperature, furnishes additional heatnecessary for dehydrogenation of butenes to butadiene and at the sametime reduces the contact time, thus preventing further appreciableconversion of the olens and diolens to polymers and/or cyclic compounds.By addition of the preheated diluent at one or more selected points inthe catalyst chamber. the temperature and contact time in both the upperand lower portions of the catalyst bed may be controlled to givethe'unit the high degree of flexibility required to process feed stocksthrough the range of naphtha and gas oil fractions.

in order to permit the coexistence of aromatiz-,y

.ing-and dehydrogenating conditions in the same catalyst bed, so as toobtain both aromatic fractions and olenand dioleiin-containingfractions, it is necessary to provide relatively long contact time inthe aromatizing zone and relazone. This is accomplished by introducingsteam tively short contact time in the dehydrogenation or otherinert-gaseous diluent, such as nitrogen,

v into that point in the catalyst bed at which the treated vapors havebeen subjected to the desired contact time'for the aromatizing reactionto have -taken place. At this point sufilcient diluent is introduced toprovide vthe desired effective dehydrogenation contact time in theremaining portion of the bed. The contact time for the crack-Ving-aromatizing'portion of the reaction is preferably between about 0.5and :iv seconds, while the contact time for the dehydrogenation portionof the reaction is between about 0.05 and 0.5 second.

Lower-boiling paramns such as methane and ethane are also relativelyinert since the reaction f may be made as This may accomplished bysuperheating the steam or other diluent to a point'suiiiciently abovethe temperature of the reactants at the point in the bed at which thediluent is introduced, to elevate the temperature in the dehydrogenationzoneto the desired point. Preferably the cracking-aromatizing reactionis carried out at a temperature between about 1100-1300 F. while thedehydrogenation reaction is also carried out at representing the optimumdepth of cracking in this process. Sumcient diluent preheated to1200-1400 F. then enters the chamber in amount sumcient to raise thevapor temperature to about 1150 F. and at the same time to reduce the 4i ed, however, that the invention should be limited to this particulartype of reactor.

Leaving the, catalyst chamber, the Lreaction mixture passcsthrough line'I with appropriate cooling by the heat exchanger l and, where steam isused as diluent, through line ,0 into the separator I from which wateris withdrawn at the bottom through line I2. The overhead vapors 'fromtheseparator are taken through line II into the accumulatori 22 whilethe normally liquid hydrocarbonmaterial'is withdrawn at the side of theseparator and taken 'through line I3 through hydrocarbon partialpressure and residence time.

In the dehydrogenation section of the catalyst bed, additional diluentmay be injected at points corresponding to temperature drops of about 50F., so that the overall temperature in the after sectionoi the catalystbed is maintained between about 110D-1150 F., and the hydrocarbonpartial pressure at about 0.05 to about 0.01 atmosphere.

Thus the point in the bed at which cracking has proceeded to an optimumextent is represented by the temperature drop off about 100LF. and atand beyond that point sufficient diluent is introduced to provide thehydrocarbon partial pressure and contact time necessary to give thedesired dehydrogenation conditions in the remainder oi the bed.

The accompanying diagram shows in conventional sideelevation oneparticular embodiment of the invention. It should be emphasized,however. that modiiications and` variations in the equipment apparent tothose skilled in the art desired without departing from the broad scopeof the invention.

With reference now to the drawing, the feed stock to the operation,which may comprise a gas oil such as that fraction boiling between 450and 650 F. and which may be obtained either by the straight distillationof a crude oil or by' the mild cracking oi a reduced crude. is ledthrough transfer line I into the iumace 2. A diluent, comprising steamor other inert gas, may be introduced by line Lheated in the furnace 2and added to the vaporized hydrocarbon. The heated mixture of gas oiland diluent then passes by line l into the reaction chamber 6 to whichan additional amount of superheated steam or other inert diluent isadded through line I to serve Vas heat carrier and to reduce the contacttime. Means are illustrated for introducing the diluent at one or morepoints in the latter portion of the bed, as desired.

I'he reaction chamber 8 may be any of various reactors known to thoseversed in the art.

'inasmuch as the invention. pertains to a novel and advantageouscracking procedure rather than to a particular type oi equipment, noattempt w ill be made to describe the catalyst chamber in detail. Anappropriate reaction vessel for use in this process, however, maysuitably be a multiple-bed type of chamber provided with suitablearrangements for the injection of heat car rier' media -at differentpoints. It is not intenda suitable heat exchange element I4 and throughline I5 into the f ractionator I8. The iractionator bottoms, comprisinggas oil and higher boiling material, are removed through line I8 whilethe overhead from the fractionator is taken through line I1 to thestabilizer I9. The stabilizer bottoms withdrawn by line 2| comprisedebutanized end-point `gasoline which, upon refractionation and furthertreatment, is suitable forutilization as a high-octane, aromaticaviation fuel.4 'Ihe overhead from the stabilizer, comprising C4 andlighter gases, is taken through line 20 to the accumulator 22. A portionof the liquid condensed in accumulator 22 andcomprsng essentially C: andC4 hydrocarbons is withdrawn through line 23 and pump 26 and returned tothe stabilizer through lines 25 and 26 as reiiux. The remainder oi theCa--Ci hydrocarbon is taken through line 21, the heat exchanger 36 andline 31, to the depropanizer 38, The gaseous material from theaccumulator 22 is taken through line 28, the compressor 28 and thecooling coil 3i to the accumulator from whence the Cz and lower-boilingproducts are 4vented to an ethylene recovery system or to the reiinerygasplant through-line Il. The liquid condensate from the accumulator Ilcomprising predominantly propane and propylene is combined through line34 with the excess reflux liquid in line 21. The bottoms from thedepropanizer, comprising the C4 ycut is taken through line 4 0 to anappropriate system II for effecting the separation of the fraction intosuch components as butadiene which is of use in the manufacture ofsynthetic rubber and into butylenes and isobutane which may be used asfeed to alkylation and polymerization processes. The amount of isobutaneavailable for these processes may be increased by the use ofisomerization reactions. The Ca overhead from the depropanizing columnmay be taken through line 39 for'further treatment or for use inalkvlation or polymerization processes.

Typical operating conditions which may be employed to carry out theprocess are approxiimately as follows: 'Ihe hydrocarbon oil change stockis vaporized in the furnace coil, being heated to temperatures markedlyhigher than those normally utilized for the production oi motor fuels bythermal treatment oi heavier oils, these temperatures employed being inthe approximate range of 1100" to 1300* F. The hydrocarbon vapors arepassed over the catalytic mass which preferably comprises anaturally-occurring material such as bauxite. Certain activatedadsorbent clays may also be used as wellas synthetic materials such asalumina or alumina admixed with minor proportions of certain activatingagents such as various metal oxides or salts. In some instances,Synthetic inaterlals ,comprising various combinations of silica gelandmetal oxidessuch as silica-alumina Vor silica-alumina-zirconia catalystsmay be suitable.

with steam or other inert gases to the extent vof about 0.5 to mols ofdiluent per mol of feed.

`Additional diluent equivalent to from to 25 mols per mol of feed,preheated .to 12001400 F.,

is inJected into the catalyst case at suitable points spaced along thecatalyst case in the direction of ilow. Since the cracking reaction isvhighly endothermic, the introduction oi.' the auxiliary heat carrierordinarily have traversed about one-third oi the length of the catalystbed. Additional injection points may be Aprovided along the lattertwo-thirds of the length of the bed. This method of operation, by virtueofthe high temperature level maintained and low partial pressure ofreactants, favors additional dehydrogenation reactions to furtherincrease oleiln and dioleiin. production. 0n the other hand, theaddition oi' auxiliary diluent greatly shortens the contact time,thereby preventing excessive polymerization and cyclization of thegaseous olens and dioleiins.

The operation may be carried out under moderately superatmosphericpressure which may range from atmospheric to about 250 pounds per squareinch gage in order that the desired contact time may be achieved for agiven diluent ratio. Ordinarily, in prder to produce increased yields oidiolens, relatively low near-atmospheric pressures are preferred, as forexample between about zero and 50 pounds gage.

In order to indicate the novelty and utility of the process, thefollowing example is given of a specic embodiment of the invention whichemploys the preferred conditionsI of temperature and pressure an'd owrate along with a prei'erred feed stock and catalyst. This example ismerely illustrative of results normally obtained and should not beconstrued as a limiting feature of the invention, as various changes inthe cata lyst and catalyst chamber design as well as modications in thereaction conditions apparent to those versed in the art may be made.

ample A 42- degee A. P. I. gravity kerosene having an initial boilingpoint of 400 F. was admitted to a catalyst chamber illled with aregenerated 10- mesh bauxite catalyst, at'a charge rate of about 1liquid volume of kerosene per volume of catalyst per hour, with steam atthe inlet in the proportion of 1 mol of kerosene to 2 mols oi steam perhour. The feed was introduced into the catalyst bed at a temperature' of1200 F. and after traversing about one-third of the bed the tem--perature at that point was found to have dropped to about 1100 F.Additional steam was introduced at this point at a temperature of 1400F. at the rate oi' 5 mols per mol of hydrocarbon feed per hour, .raisingthe temperature to 1150 F. When the hydrocarbon-steam mixture hadtraversed approximately another third of the bed the temperature dropwas about 50 F. and at this point additionalsteam at a temperatureofabout 1400 F. and a rate of about 8 mols per hour per mol of hydrocarbonfeed was introduced. The eilluent product left the bed at a temperatureof about 1100 F. Fractionation of the eilluent yielded a C4 fractionamounting to 11.5 per cent by volume of the charge and of this fraction32 per cent by volume was butadiene, while -04.3 per cent of thefractionconsisted of butenes. of which occurs after the charge vapors andaromatic content.

carbons which comprises vaporizing and heating 35 per cent wasisobutylene. The C: fraction accounted i'or 17.5l volume per cent of thecharge and was about v92 `per cent propylene. The C: Y fractioncomprised 75 per cent ethylene and.

amounted to 30 volume per cent of the charge.

Butane-free gasoline was obtained in ayield of about 24.5 volume percent of the charge. The olearlA. S. T. M. octane number `of the gasolinewas 82.5 while the Research octane of the un.

leaded gasoline was 96.0. A high aromatic content or the gasoline isindicated by the refractive index of 1.4795. I

' .In the above example the operation was carried out at a pressure of 5pounds per square inch gage and 'for a process period of six hoursduration.

Another portion oi' the same-feed lstock was catalytically crackedunderidentical conditions except that 9.3 mols of `steam diluent per molot hydrocarbon was initially introduced with the feed and no furtherdiluent was added. On fractionation a C4 fraction amounting to 10.3volume per cent of the charge was obtained and of this fraction 22.6volume per cent was butadiene and 67.9 per cent was butenes. Of thebutenes frac- 'tion 37 per cent was isobutylene. 'I'he C: fractionaccounted for 16.5 volume per cent of the feed of which about 90 percent was propylene. The C2 fraction amounted to about 29 per cent of thecharge and contained about 72 per cent ethylene.

A butane-free gasoline amounting to 25.2 per cent of the charge byvolume was obtained and the clear A. S; T. M. octane number of thegasoline was 81.6 while the Research octane of the unleaded gasoline was95.0. The refractive lndex was 1.4780.

production is increased about 50%, andsomewhat greater overallproduction of olefins is also obtained. Slightly less of abutane-i'reegasoline n is obtained, but this has a somewhat higher octane number dueto the slightly greater olefin Weclaim:

l. A process for the conversion ofv a. normally liquidhydrocarbondistillate to an aromatic fraction and normally gaseous unsaturatedhydrothesaid distillate to a temperature of 11001300 F. passing saidvaporized distillate in contact with a solid adsorbent cracking anddehydrogenating catalystnfor a contact time of 0.5 to 3 seconds,injecting sufllcient steam preheated to 11001400 Ill'.` at a pluralityof points spaced along/the length of the catalyst bed in the direc-vtion of vapor now after the initial contact period to allow thedistillate a further contact time of 0.05 to 0.5 seconds with saidcatalyst, and separating butadiene, normally gaseous oleilns and anaromatic fraction fromv the eilluent.

2. The process of claim 1 in which the preheated steam is introduced atsaid points in the catalyst bed in a volume and at a temperaturesumcient toraise the temperature to 110D-1150 F. in

the dehydrogenation zone and to maintain the` temperature in a range of50? F. Y

3. The process of claim 1 in which the crack- .70 ingand-dehydrogenation catalyst is bauxite.

the said distillate to a temperature 01'1100-1300 4. A process for theconversion of a normallyI liquid hydrocarbon distillate to an aromaticfraction and normally gaseousl unsaturated hydro? carbons'"'whichcomprises vvaporizing and heating 1100-1400 F. at a plurality oi Pintsspaced 5 alonx the length of the catalyst bed in the direction of vapornew after the initial contact period to allow the distillate afurthercontact time oi 0.05 to 0.5 second with said catalyst and separatin:said normally gaseous hydrocarbons and said i0 aromatic fraction fromthe eilluent.

The followirrg references are of record in th me of this patent:

, UNITED BTA PA Number Name Date Schulze Feb. 25, 1941 Howard Aug. 5,1941 Eglot May 12, 1942 Houdry Aug. 17. 1943 Ruthru Mar. 2,1944 SheppardMay 2, 1944 Schulze etal July 11. 1944

